<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Custom variables</title>
  <style>
    :root {
      /* Place variables within here to use the variables globally. */
      --some-color: #da7800;
      --some-keyword: italic;
      --some-size: 1.25em;
      --some-complex-value: 1px 1px 2px whitesmoke, 0 0 1em slategray, 0 0 0.2em slategray;
    }
    .custom-variables {     
      color: var(--some-color);
      font-size: var(--some-size);
      font-style: var(--some-keyword);
      text-shadow: var(--some-complex-value);
    }
  </style>
</head>
<body>
  <p class="custom-variables">CSS is awesome!</p>
</body>
</html>